Incandescent filament



Patented Apr. 5, 192 7.

UNITED STATES PATENT. OFFICE.

GORTON R. FONDA, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPAR'Y, A CORPORATION OF NEW YORK.

INOAN DESCEN T FILAMENT.

R'o Drawing.

The present invention relates to a novel refractory metal composition or' alloy com sisting largely of tungsten and containing thorium and copper as-constituents, which 5 is of particular utility as a lighting body in -incandescent lamps. Filaments embodying .my invention have a materially lower vapor pressure than an ordinary tungsten filament, and hence may be operated with a higher .10 lighting .efficiency than tungsten with the same average length of life, and if operated at the same elficiency will have a longer life. Although the production of my new incandescent material is not limited to any particular process, I find it convenient to employ .in general the method of Coolidge U.- S. Patent No. 1,082,933 of December 30, 1913. Thorium and copper may be added to tungsten in an elementary state, or as reducible or decomposable compounds. The following examples of tungsten composi; tions containing thorium and copper material will illustrate my invention.

To the finely divided metallic tungsten may be incorporated by weight 0.5% metallic thorium and-0.25% co per. This mixture is sintered and swage as described in the above Coolidge patent whereby the material is rendered ductile. It is then drawn so into filaments as described in this patent.

"The product when subjected to swa-ging and drawing has normally the'small grain structure characteristic of thoriated tungsten wire, as described in Coolid e Patent No. 3 1,082,933. The specific electrical resistance ofthe swaged metal is materially higher than the s ecific resistance of substantially pure meta lic tungsten, thoriated or nonthoriated',--say, in the neighborhood of 10% tungsten. At a given temperature the rate of evaporation of tungsten containing thorium and copperis less than 'that of either substantially pure tungsten or tung- Application filed Kay 1, 1923. semi No 635,970.

sten containingthorium alone. Incandescent filaments made in accordance with my invention may be mounted in vacuum lamps or in lamps containing a filling of gas or vapor, as described in Langmuir Patent No. 1,180,159. When filaments embodying my invention are to be operated in gas-filled lamps potassium silicate preferably is added to the raw batch-of filament mix, as described in ,Patent No. 1,410,499,- granted to Aladar Pacz, March 21, 1922.

What I claim as newand desire to secure by Letters Patent of the United States, is:

1. A composition consisting of tungsten in preponderating amount and containin fractional percentages of thorium an 1 copper.

2. A "sintered metal composition consisting in preponderating amount of tungsten and containing by weight about 0.50%

thorium and 0.25% copper.

3. A filamentary body consisting largely of tungsten and containing associated therewith thorium and copper, said filament having at a given temperature of incandescence a rate of evaporation materially lower than substantially pure tungsten.

4. An incandescent lighting body operable at incandescence whlch consists in preponderating amount of tungsten and contains thoriumr and copper in combined amount ofless than one per cent.

5. A metal composition consisting of a preponde'rating amount of tungsten and containing suliiciently large amounts of thorium and copper to cause the .electricalresistance 80 to be increased and the rate of evaporation at a given high temperature to be decreased v as compared with tungsten unassociated with I 4 higher. It is substantially as workable as said materials.

In witness whereof, I have hereunto .my hand this 30th day of April, 1923.

GORTON R. FONDA. 

